[2015 Spring Life Sciences & IBB Regular Seminar]
       
         
     ▶Subject: Regulatory roles of the phosphoenolpyruvate-dependent sugar transport system in bacteria
       
     ▶Speaker: Prof. Yeong-Jae Seok 

                     (Department of Biophysics and Chemical Biology, Seoul National University)
               
     ▶Date: 4:00PM/May/1(Fri.)/2015
        
     ▶Place: Auditorium(1F), Postech Biotech Center
       
             *Abctract
           The bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) is a multicomponent system that participates in a variety of physiological processes in addition to the phosphorylation-coupled transport of numerous sugars. In Escherichia coli and other enteric bacteria, enzyme IIAGlc (EIIAGlc) is known as the central processing unit of carbon metabolism and plays multiple roles, including regulation of adenylyl cyclase, the fermentation/respiration switch protein FrsA, glycerol kinase, and several non-PTS transporters, whereas the only known regulatory role of the E. coli histidine-containing phosphocarrier protein HPr is in the activation of glycogen phosphorylase. Because HPr is known to be more abundant than EIIAGlc in enteric bacteria, we assumed that there might be more regulatory mechanisms connected with HPr. The ligand fishing experiment in this study identified Rsd, an anti-sigma factor known to complex with σ70 in stationary-phase cells, as an HPr-binding protein in E. coli. Only the dephosphorylated form of HPr formed a tight complex with Rsd and thereby inhibited complex formation between Rsd and σ70. Dephosphorylated HPr, but not phosphorylated HPr, antagonized the inhibitory effect of Rsd on σ70-dependent transcriptions both in vivo and in vitro, and also influenced the competition between σ70 and σS for core RNA polymerase in the presence of Rsd. Based on these data, we propose that the anti-σ70 activity of Rsd is regulated by the phosphorylation state-dependent interaction of HPr with Rsd.
On the other hand, flagellar motility is one of potential virulence factors in many pathogenic bacteria. Although the presence of preferred sugars such as glucose has been known to prevent flagellar motility in some bacteria, the underlying molecular mechanism remains unknown. Here we uncover the mechanism of glucose-mediated inhibition of flagellar motility in Vibrio vulnificus, a human pathogen causing septicemia. In the presence of glucose, enzyme IIAGlc (EIIAGlc) of the phosphoenolpyruvate:sugar phosphotransferase system inhibits the polar localization of FapA (flagellar assembly protein A) through a direct interaction. A loss or delocalization of FapA resulted in a complete failure of flagellar synthesis and motility. However, when glucose is depleted, EIIAGlc is phosphorylated and releases FapA. Free FapA is then localized back to the pole, where it activates the flagellar assembly. Together, these data provide new insight into a bacterial strategy to reach and stay in a glucose-rich environment.

     ▶Inquiry: Prof. Hwang, Cheol-Sang (279-2352)
             
       
       * This seminar will be given in Korean.
   please refrain from taking photos during seminars. *